1) Slang/Nickname, for someone with the name Thomas or Tom, due to the similarity in pronunciation. In no way is it meant to be taken as offensive, more a boisterous greeting.

2) A description of someone who gets screwed over by every single friend he/she has, even those that are considered good friends will have attempted to deceive a person of this description. This person may also be subject to frequent betrayal by so-called 'friends'. *

*Note - not always successfully.

3) A person whose 'friends' all try to use at some point in time for their own personal gain, but is never repaid for the favour in any shape or form. Also these 'friends' may frequently 'forget' to ask this person to be present at any gatherings, maybe in spite, jealousy or plain ignorance.

Finally…
4) Somebody who is independent of others and who does not imitate others in an attempt to be 'popular' by following every single 'trend' or 'whim'.